Introduction: Van De Graaff Electrostatic High Voltage Generator
Step 1: The Parts for the VDG
The only parts in this that you are not likely to find at your local hardware store are the wheels. I used bed frame wheels. their choice sorta dictated the size of Van De Graaff (Henceforth called VDG for short.) More about the wheels later.
These are the parts used.
1 Lightbulb socket (I pried out the bottom most contact, to give less surface area to bleed off static charges.
1 Large globe lightbulb
1 1.50"" to 2" pvc adapter (lightbulb socket fits in here nicely, and gives space to mount the brushes)
1 2" to 3" pvc adapter
1 3" to 3" PVC Coupler
1 5" threaded rod and assorted washers and nuts, I think it was 5/32"
1 6" threaded bolt, and washers, small enough for the wheel to glide on)
2 slightly curved plastic bedframe rollers. (was going to use skateboard wheels sanded down on my drillpress, but my dad had these in his shop)
1 3"x3"x1.50" PVC Tee
1 length of pvc (Ihad to use ABS which is not as good due to its carbon content, but it was all I could find in precut lengths, and didnt want to buy 9 more feet of pipe.
1 1.50" to 0.25" pvc adapter
2 sets of skateboard wheel bearings,
Some copper wire both to make a ground wire, and a spark wand wire, but also to make the brushes.
1 outlet plug (this is only connected to the ground pin
1 can of cold galvanizing spraypaint
1 can of copper metallic spraypaint
1 drill socket adapter. (to turn the bottom wheel)
1 drill, (optional speed controller)
1 sheet of latex exercise banding
1 tube of bike tire patch glue.
Teflon pipe tape,
copper foil tape
Other misc Stuff, A board to screw it down to and some long screws. and A binding post for the charge wand, some wire, a old junk drawer nob pull for the wand, some plastic tubing for the shaft of the wand.
Step 2: The Globe
From that other VDG instructable I mentioned in the first page, i got the idea to use a lightbulb, but i knew the foil covering they used was inefficient, (too many bumps and corners)
I went with a large 8" decorative bulb. And then I set about trying make the glass (an insulator) conductive on the surface. This involved trying to find out what spray paint was static conductive.
Sadly most is not! after trying various paints on glass jars, i finally settled on a very high zinc content "Cold Galvanizing" Spray, from Rustoleum this makes for a nicely conductive but ugly. globe
In my experiments Rustolium decoratives Metallic Copper spray was also fairly conductive. so i sprayed a topcote with that to make it more touchable and pretty. (tested with and without both worked pretty well.
*I tried also making a rig to electro plate copper onto the zinc, and while i had soem success, the chemicals involved in the paint kept corrupting my plating solution, im going to try again with conductive plating paint. someday! And probably do a new instructable about making copper spheres out of lightbulbs.
Step 3: Upper Wheel
As indicated in the graphics on the parts page,
Saw two notches in the 3" down to the center line on the PVC Coupler, verify your threaded rod can fit down in it nice and level.
Assemble one of the wheels onto the 6"bolt , and put washers and nuts on both sides. slide it down into the notches. and finger tighten the nuts on the outside of the fitting. (you will need to slide this out of the notches when putting the belt on.
Using a few drops of superglue, glue some pvc Teflon tape to the upper wheel and cover it in about 2 layers of Teflon, superglue down the remaining tail
also go ahead and assemble the other parts, the lightbulb socket, and the 1.50" adapter and the 2-3" adapter, install loops of bare stranded copper wire around the single screw left in the light socket, once affixed, snip open the loops to make lots of copper brush bristles, bend/shape them to just glide over the wheel/belt to pickup the static charge and transfer it to the socket/and eventually to the lightbulb/globe
Step 4: Lower Wheel Assembly.
For the lower shaft, its only supported on one side, (to aid with installing the belt later)
You need to press the skate barrings into the 1/2" to 1" adapter this will serve as support for the bottom wheel., i used some wood and my vice to squeeze them in, one after the other.
You also need to figure out where you want the wheel to ride in the PVC Tee adapter best is about center, mark the threaded rod and place your wheel where it needs to go, (you need about 1" or more rod to stick out through the bearings to power it with.
Now tighten on lock washers and nuts on either side of the wheel sandwiching it and making it turn when the threaded rod is turned
wrap the lower wheel in copper foil tape and insert into tee and out through the fitting with the bearings. snap it into place.
Now make and install your brushes, We made some loops of stripped stranded wire, and wrapped them around a screw and put them into the bottom of the tee fitting and snipped the loops to make lots of little broom bristle like brush points just grazing the side of the bottom wheel
Step 5: Starting the Assembly.
Step 6: Continued Assembly
For stability and ease of use, I screwed it down to a square chunk of plywood. just drilled some holes in the lip of the OVC tee, and installed long screws into the wood.
At this time we also drilled a hole for a ground wire to go tho the brushes, and also to the charge wand. Both were run to a binding post we mounted on the board.
At this point you are about all ready to go, you are going to need atleast one other person for the next step.
Step 7: Assembly
Prepare by removing the top roller by just sliding the axle up the sawed out notches. and set it aside,
you will also need a long semi rigid wire to fish the belt up the tube with, (a untwisted metal coat hanger would work well, I used some stiff copper wire.
make a hook out of your coathanger,
Put the top coupler on the top of the pipe, and insert the coathanger hook down the pipe.
place the belt (still using gloves) around the lower wheel, now hook the belt with the coathanger hook, and while standing up the PVC pipe, keep tension, upping the belt up through the top fitting, look down to make sure there is no twist or roll in the band. Have your friend hold the coathanger up while you thread the upper wheel/axle through the band and let it carefully down into the notches. when done it should look like a big conveyor belt. tighten the upper bolts and give the lower shaft a quick spin with your fingers.
The curved (domed) shape of the wheels should keep the belt centered. but you might have to pre-center it a little bit. make sure it does not keep wandering too far to one side or the other. this may indicate your shafts are not parallel and you will have to shim or fix, that.
Step 8: Done!
Lots of folks played with it during our big February event at our Hackerspace Quelab.
If you are ever in Albuquerque! Look us up!
Thanks and Enjoy!
Finalist in the
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